Sex-Dependent Effects of Bmal1-Deficiency on Mouse Cerebral Cortex Infarction in Response to Photothrombotic Stroke

Stroke is a leading cause of disability and death worldwide. There is increasing evidence that occurrence of ischemic stroke is affected by circadian system and sex. However, little is known about the effect of these factors on structural recovery after ischemic stroke. Therefore, we studied infarction in cerebral neocortex of male and female mice with deletion of the clock gene Bmal1 (Bmal1-/-) after focal ischemia induced by photothrombosis (PT). The infarct core size was significantly smaller 14 days (d) as compared to seven days after PT, consistent with structural recovery during the sub-acute phase. However, when sexes were analyzed separately 14 days after PT, infarct core was significantly larger in wild-type (Bmal1+/+) female as compared to male Bmal1+/+ mice, and in female Bmal1+/+, as compared to female Bmal1-/- mice. Volumes of reactive astrogliosis and densely packed microglia closely mirrored the size of infarct core in respective groups. Estradiol levels were significantly higher in female Bmal1-/- as compared to Bmal1+/+ mice. Our data suggests a sex-dependent effect and an interaction between sex and genotype on infarct size, the recruitment of astrocytes and microglia, and a relationship of these cells with structural recovery probably due to positive effects of estradiol during the subacute phase.

The AGES-Reykjavik Study suggests that change in kidney measures is associated with subclinical brain pathology in older community-dwelling persons

Decreased glomerular filtration rate (GFR) and albuminuria may be accompanied by brain pathology. Here we investigated whether changes in these kidney measures are linked to development of new MRI-detected infarcts and microbleeds, and progression of white matter hyperintensity volume. The study included 2671 participants from the population-based AGES-Reykjavik Study (mean age 75, 58.7% women). GFR was estimated from serum creatinine, and albuminuria was assessed by urinary albumin-to-creatinine ratio. Brain MRI was acquired at baseline (2002-2006) and 5 years later (2007-2011). New MRI-detected infarcts and microbleeds were counted on the follow-up scans. White matter hyperintensity progression was estimated as percent change in white matter hyperintensity volumes between the two exams. Participants with a large eGFR decline (over 3 ml/min/1.73m2 per year) had more incident subcortical infarcts (odds ratio 1.53; 95% confidence interval 1.05, 2.22), and more marked progression of white matter hyperintensity volume (difference: 8%; 95% confidence interval: 4%, 12%), compared to participants without a large decline. Participants with incident albuminuria (over 30 mg/g) had 21% more white matter hyperintensity volume progression (95% confidence interval: 14%, 29%) and 1.86 higher odds of developing new deep microbleeds (95% confidence interval 1.16, 2.98), compared to participants without incident albuminuria. The findings were independent of cardiovascular risk factors. Changes in kidney measures were not associated with occurrence of cortical infarcts. Thus, larger changes in eGFR and albuminuria are associated with increased risk for developing manifestations of cerebral small vessel disease. Individuals with larger changes in these kidney measures should be considered as a high risk population for accelerated brain pathology.